April 1, 2001
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967 or

April 10, Tuesday, 2-5 pm, Killdeer Farm, Norwich

This is the 20th season that Jake and Liz Guest have been growing crops at Killdeer Farm. They have 9 greenhouses and high tunnels for the production of their own vegetable transplants, as well as bedding plants, hanging baskets and greenhouse tomatoes for retail sale at their farm stand. Jake has long been experimenting with biological controls and cultural practices to manage pests like thrips. Maragaret Skinner and Michael Brownbridge from the UVM Entomology Lab will join us in a discussion of greenhouse IPM strategies, including scouting procedures, pest identification, and use of bio-rational pesticides. Directions: Take exit 13 (Norwich) off I-91 onto route 5 north. Stay on route 5 for about 2 ½ miles. Just after the vet clinic on left, turn left onto Butternut Rd. The farm is at end of road.

Adapted from an article by Hugh W. Fraser, K. Helen Fisher & Ian Frensch, OMFRA
Bird damage to tender fruit is a serious problem for many growers. Some birds that cause problems in fruit crops include: robin, starling, grackle, gull, blackbird, grackle, gull, finch, oriole, cedar waxwing and mockingbird. It is important to know how birds behave in order to control them. Here are some facts about bird behavior: Large flocks of birds are easier to scare than small ones. Bird damage patterns can vary considerably from year to year and from farm to farm. Bird damage is usually localized and not uniformly distributed throughout an area. Birds are opportunists, feeding on whatever is available. It is difficult to break birds of the habit of feeding in a particular area once they are established. Birds establish their home territory in late April and May and often remain in the area until the crop ripens. Crops near roosting or nesting areas, woodlots or ponds are more vulnerable than those in the open. Birds acclimate quickly to uniform movements or noise patterns. Different species of birds respond differently to various repellent methods. Birds can be diverted to other nearby feeding areas. Birds will endure significant hardship to feed. Birds often follow the same flight patterns to feed. Birds usually feed early in the morning around sunrise and late in the afternoon around sunset. Birds like to drink water when they feed. Some birds travel in migratory flocks, while others fly in from local woods. Birds feeding on your crop will attract other birds, compounding the problem. The sweeter and earlier the variety, the more  attractive it is to the birds. Even if crops are protected with netting, birds may perch on the nets and feed through them or find small holes.
There are four types of bird repellent methods currently available to growers: acoustical repellents, visual repellents, physical exclusion, biochemical repellents. An integrated approach, using a variety of these repellent methods is needed.

Acoustical repellents rely on sound to scare birds away. Birds have a hearing range similar to humans, so if people can hear it, birds can hear it. Unlike rodents, birds cannot hear ultrasonic sounds. The most familiar acoustical bird repellent equipment is the propane-fired cannon that produces loud, unexpected blasts. These vary from mechanical single-shot units, to fully electronic, randomized, rotating multi-shot units. The latter are the most effective over the long term, since the timing and direction of the blast is truly random and the birds do not know when or where the next blast will occur. Although the loudness of the blast is important, it is the unexpected nature of the blast that keeps birds nervous. Birds quickly get accustomed to units that are stationary, shoot at regular intervals, or fire very rapidly. More blasts are not better. Unfortunately, neighbors never get used to propane-fired cannons. Guidelines on the use of propane-fired cannons are: Set at intervals greater than 3 minutes. Use between sunrise and sunset when birds feed. Operate no more than one unit per 5 acres, unless it is absolutely necessary. Ensure that propane tank valves do not leak, as this can cause units to blast unintentionally, even when they are shut off. Move the units around to keep the birds off-guard. Use electronic clock timers that automatically shut off the units.
Electronic sound devices can be less irritating to neighbors than propane cannons. There are two types used to broadcast electronic synthetic sounds to repel birds: random noises, irritating to birds (traditional), and distress calls that mimic individual bird species. The traditional electronic sound device is often referred to as the AV Alarm, a trade name that has been familiar in the industry for 30 years. This makes an electronic, warbling sound that interferes with the bird's sensory system, making birds uncomfortable and insecure. In some cases, the birds are unable to communicate with each other and will leave the area. These units work well when used in a combination with propane-fired cannons. The electronic sound device keeps the birds irritated and edgy, while the cannon provides the stimulus to drive them away. A new generation of electronic sound devices uses digital technology to produce distress calls of specific birds. They are only effective against the bird species whose distress calls are encoded on the microchip. However, some residual repellent effect may be noticed on species that normally travel together with the target birds. Some farmers report that digital units also attract birds of prey, such as hawks, who misinterpret the electronic distress calls for the real thing. Hawks circling the farm will also scare away birds. Even though these units produce electronic bird distress calls,  they sound to us like real birds, and are usually not as   objectionable to neighbors. These devices also produce a lower decibel sound level than the more traditional units. Both types of electronic sound devices can be used to discourage birds from nesting in nearby trees in the spring.
Whistling and/or pyrotechnic cartridges are launched from a hand-held pistol and produce a loud, whistling sound throughout their flight. There is also a delayed reaction banger cartridge that travels through the air in silence, then explodes high in the air near flocks of birds as they are flying with the same sound level as a propane-fired cannon. Shooting these ear-piercing sounds into a flock of birds works well as a repellent, and can quickly clear a field, woodlot or transmission line before the flock lands on the crop. They may be the most effective manual scaring device available. Shotguns are often used to repel birds, but they are not as effective as launching the sound directly into the flock like the pyrotechnic units. Although shotguns might provide a frustrated grower with a form of stress relief, even an excellent marksman will never seriously reduce the bird population. Many other sound producing devices or strategies have had only limited success, including air horns, clanging aluminum pie plates, shiny flashing metal objects, firecrackers and Mylar humming lines. These devices generally work only for a few days before the birds start to ignore them again. They might be most effectively used in the days just before harvest when bird pressure is the greatest.
Visual Repellents are usually add-ons to acoustical systems, and are rarely sufficient by themselves. Birds generally have very good eyesight and react to both movement and things that resemble their enemies. However, birds do not react nearly as much to visual deterrents as they do to acoustical ones. Scare-eye balloons with their graphics depicting the gaping mouth of a hawk have proven themselves worldwide. They are manufactured in white, black and yellow. For Ontario, the best bird scaring results have been with yellow scare-eye balloons. Blackbirds do not like the color yellow. Sparrows and finches are repelled to a lesser extent, while robins and cedar waxwings are hardly repelled at all. Scare-eye balloons must be suspended above the crop and must move freely with the wind to look more realistic.
Streamers and flashtape are strips of shiny plastic tape which are strung over crops. They move with even the slightest breath of wind and also reflect sunlight. From above, the birds view an entire vineyard or orchard that appears to be in motion. Flashtape is available in yellow for blackbird species and in a red/silver combination for repelling a broad range of species. It is especially effective to string streamers and flashtape along perimeter rows where the most severe damage occurs, or in other areas that need additional protection. Some bird species, notably starlings, are repelled by flashing lights and mirrors. Flashing lights are only effective at dawn or dusk when the natural light is dim, and mirrors are only effective when the sun is shining. Some growers have mounted mirrors on top of rotating propane-fired cannons and from above, the mirrors appear to be moving. Farmers have reported a repelling effect on sunny days. Hawk silhouettes, stuffed owls and snakes have only a limited effect for a short period of time. Some farmers report they have seen birds nesting right on these devices.
Netting is the best way to ensure crop protection. Unfortunately, it is usually the most expensive option, although the cost of netting material has been dropping over the years and the systems for applying the nets are improving. Nets offer virtually 100% bird protection and help maximize yields. Bird netting is available in a lightweight one-use formulation or heavier multi-use ultraviolet protected materials. There are rigid or stretch materials and different widths and mesh sizes. Draping the net directly over the crop is best suited for crops which do not require multiple pickings, such as grapes. It is labor intensive to both install and remove netting that tangles with the plant. Overhead netting systems are  most effective for blueberries, dwarf  sweet cherries or high value wine grapes in heavy bird-pressure areas. Nets must be removed or at least retracted at the end of the season to protect them from ultraviolet degradation and snow loads.
Chemical repellents have come and gone over the years, partly due to lack of effectiveness, but also because of adverse health side-effects. At present, there are no effective, food grade chemical bird repellents registered for use.

Many growers hope that there is a single magic solution to their bird control problems. Other than netting, using only one deterrent system will not work. However, using existing bird control methods more effectively may be all that is needed; use an integrated approach, start early with a control program, and avoid predictable control patterns. Consider the following when planning a control strategy: Use scaring methods in combinations that disrupt the bird's sense of sight, sound, and instill fear. New and unfamiliar control methods work well initially, but decline in effectiveness over time. Devices with different scaring techniques complement each other. Random, unexpected noise is always better than predictable, patterned noise. Position more scaring devices along the perimeter of fields, near trees/ponds, and at flight pattern entry areas. Farms along hill faces benefit from the echoing effect of propane-fired cannons and electronic sound devices. Use prevailing winds to your advantage to maximize sound dispersal. Electronic sound devices and propane-fired cannons should be installed to direct sounds as close to the fruiting zones as possible. Once birds have a taste of your delicious crop, it is difficult to break their habits. Therefore, you must stop the birds from getting an initial foothold on the farm. During the nesting season, some birds can be convinced to settle elsewhere by using electronic bird scarers in the nesting area. Come harvest time, growers often start their bird control program too late, after the birds have already tasted the crop. Bird control equipment must be in place at least 10 days before the crop is attractive to the birds.